(1) Field of the Invention
The present invention relates to a high power semiconductor laser device that is capable of outputting laser light of high power and is suitable for optical recording, optical communication, welding, and the like, and to a multiple wavelength laser light emitting apparatus employing the high power semiconductor laser device.
(2) Related Art
In recent years, a great deal of research has been made to develop high power semiconductor laser devices used as light sources for optical recording, optical communication, welding, and the like.
One example of such semiconductor laser devices is disclosed in Japanese Laid-Open Patent Application No. H05-226765. A technique disclosed therein is for emitting laser light using a semiconductor laser array element as a light source, the semiconductor laser array element having an array structure in which a plurality of laser light oscillators are formed in stripes on one substrate.
According to this technique, the plurality of laser light oscillators are made close to each other on the substrate, so that energies filter through each of the laser light oscillators and are combined together, resulting in phases of laser beams emitted from end faces of the laser light oscillators being synchronized. Accordingly, the laser beams emitted from the end faces of the laser light oscillators can be easily condensed on one spot using an optical lens or the like, realizing output of high power laser light.
With the above technique, the laser light oscillators are connected to each other through the energies filtering through each of the laser light oscillators. However, such energies are spread in an extremely small range of some microns, and therefore, the laser light oscillators should be located extremely close to each other in a narrow space. This poses restrictions for the design of a semiconductor laser device, such that a width of a current blocking layer is to be made narrow, making manufacturing of such a semiconductor laser device extremely difficult. Also, as the laser light oscillators are located close to each other, heat is confined within narrow spaces, making heat generation more active. Rise in temperatures is particularly remarkable at the central part of the semiconductor laser device, which might cause dissolution or thermal expansion of the semiconductor laser device, the thermal expansion causing changes in the wavelength of laser beams. This could undermine reliability of the semiconductor laser device. Furthermore, this semiconductor laser device also lacks in stability as energies filter through the laser light oscillators unevenly. To avoid such problems, setting a width of a current blocking layer wider to make an interval between adjacent laser light oscillators larger can considered, in disregard of making phases of the laser beams synchronized. However, in this case, the laser beams can not be condensed on one spot, and accordingly output of high power laser light cannot be achieved.
Also, a plurality of such semiconductor laser array elements maybe used as a light source in an attempt to increase the total amount of light and achieve output of high power laser light. However, in this case, only a certain level of output can be achieved, because phases of laser beams emitted from one semiconductor laser array element cannot be synchronized with phases of laser beams emitted from other semiconductor laser array elements.